"It is such an honor to be able to play this iconic role," Watts said in a statement. "Princess Diana was loved across the world and I look forward to rising to the challenge of playing her on screen."

The movie will also focus on Diana's little-known but epic romance with Dr. Hasnat Khan, who many considered to be the real love of her life -- not billionaire Dodi Al-Fayed, whom she was dating at the time of the crash and died with her.